[$200] Expose Swagger at /docs endpoint

[rootelement]

Like the v5 Challenge API
http://api.topcoder-dev.com/v5/challenges/docs

Also, if I load the current swagger on the develop branch into editor.swagger.io, it has all kinds of errors at the top:
b08cf17#diff-3933d49df39e665e1db0e420518b7c20

Tasks

• Fix errors in swagger
• Use swagger-ui-express to expose the swagger in /docs

[callmekatootie]

Assigned to @xxcxy

[callmekatootie]

Changes in develop branch.

PAID https://software.topcoder.com/review/actions/ViewProjectDetails?pid=30175806